A website from UGA Cooperative Extension

by Carole MacMullan, Fulton County Master Gardener Extension Volunteer

This article is part of Garden Buzz, a series from Appen Media and the North Fulton Master Gardeners, where rotating columnists explore horticulture topics like herbs, insects, and wildlife conservation. Find all Garden Buzz articles here.

In March 2020, Americans became keenly aware of a fast-spreading, globally transmitted disease called COVID-19. Soon, “pandemic” became a household word, and everyone became concerned about its transmission and possible deadly consequences.

Most Americans in 2020 never encountered a disease that had spread so rapidly and had such dark consequences. Going back in history, in 1952 there was an epidemic of polio, a viral disease that attacks the human nervous system. As a result of donations to the March of Dimes and the discovery of the Salk and Sabin vaccines, the risk of a polio pandemic in the U.S. is now zero! 

Reaching further back into history, you probably remember studying about the Spanish Flu Pandemic of 1918-19 and the Bubonic Plague that rapidly spread throughout Europe, killing an estimated 50 million people, or 50 percent, of the European population in the 1300s and 1400s.

Pandemics are not isolated to humans. Pandemics have ravaged the population of a wide variety of plants and animals as well. I would like to concentrate on three tree pandemics.

American Chestnut

As a child, I lived near a mountain range in western Pennsylvania called Chestnut Ridge. Even though we hiked in the forests near our house, I never saw a chestnut tree. Soon, I became curious about the catastrophic loss of the American chestnut tree in the wild. Before 1930, an estimated 4 billion American chestnut trees existed in the forests of the eastern U.S. These trees were the dominant hardwood species, and their large, high energy content chestnuts provided a food source for a wide variety of insects, microorganisms, birds and mammals.

The chestnut forests were rapidly changed by a microscopic package of bad news! A dying American chestnut tree was first observed in the Brooklyn Botanical Garden in 1904. It promptly was determined to have been infected by a foreign invader, a fungal disease that was given the common name American chestnut blight. 

American Chestnut Tree with disease canker caused by the American Chestnut Blight taken at Berry College. Image by the author.

Fungal diseases can spread rapidly because they reproduce by microscopic spores. The wind spreads these species-specific, microscopic messengers of death quickly. In three short decades, the wind carried the chestnut blight spores throughout the entire eastern U.S., causing an American chestnut pandemic. By 1930, so many American chestnuts died from blight that the logging industry began to clear-cut all the remaining healthy American chestnuts, devastating Appalachian forest ecosystems from Maine to north Georgia and Alabama. By 1940, they were declared extinct in the wild. This event has been described as the “most devastating forest event ever!”

Today if you walk in any eastern U.S. forest, you will find that oak trees now occupy the habitats once populated by the life-sustaining American chestnuts. Nutritious, high-energy acorns produced by over 70 species of oak trees, 28 of which inhabit the forests of Georgia, now sustain a diversity of microorganisms, insects, amphibians, reptiles, birds and mammals. As a result, oak trees are now the dominant or keystone trees of eastern U.S. forests. 

American Elm

There are more than 30,000 Elm Streets in the United States and many town and city parks, such as Central Park in New York City, that enjoy the beauty and cascading form of the American elm tree. These highly desirable urban trees also encountered a deadly fungal disease, Dutch elm blight. As the name suggests, the disease was first detected in the Netherlands in 1921 and was introduced to the U.S. for the first time in the 1970s. Many towns were forced to cut their streetscape trees. Currently, my hometown of Westmont, Pennsylvania, has the longest continuous tree-lined street of American elms in the United States. Luzerne Street is home to approximately 195 well-tended American elm trees. 

Through the efforts of selective breeding for resistance to Dutch elm blight, two new, disease-resistant elm hybrids are now available. Additionally, the American Chestnut Society is engaged in a two-pronged approach using both selective breeding and bioengineering with the goal of creating a healthy, viable and disease-resistant American chestnut. The hope is to create hybrids of both species that will grow and thrive in their former habitats.

Southern Pine Beetle

One of the most common forest diseases facing Georgia landowners and foresters is the Southern pine beetle. Pine beetles bore through the bark of pine trees and create tunnels as they consume the xylem tissue that makes up the annual rings. Without the xylem tissue needed to transport water throughout the tree, the tree will die. Since I moved to Milton in 2008, I have witnessed the death of hundreds of young, venerable pine trees in the forest behind my house. If you see a pine tree with peeling bark and exposed tunnels made by the pine beetles, please consult an arborist to confirm the extent of the beetle infestation. If confirmed, please take action to destroy and remove the tree or trees from your yard to prevent the spread of this disease that is devastating our southern pine forests.

Pine Bark Beetles graphic. Image by Lacy L. Hyche, Auburn University, Bugwood.org

Let me end with this quote:

We are all interconnected – people, animals, our environment. When nature suffers, we suffer. And when nature flourishes, we all flourish.”  Dr. Jane Goodall

Happy gardening!


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About the Author

portrait of the author

This week’s “Garden Buzz” guest columnist is Carole MacMullan, a Milton resident and Master Gardener since 2012. Carole describes herself as a born biologist. Since childhood, she loved to explore the out-of-doors and garden with her mother. When she entered college, she selected biology as her major and made teaching high school biology her career for 35 years.  Shortly after moving from Pittsburgh, she became involved with the philanthropic mission of the Assistance League of Atlanta (ALA), and in 2014, completed the Master Gardener program and joined the North Fulton Master Gardeners (NFMG) and the Milton Garden Club. Carole uses her teaching skills to create a variety of presentations on gardening topics for the NFMG Lecture Series and Speakers Bureau.